FIG. 1 depicts schematically an example of a heavy vehicle 100, e.g. a truck, bus or the like. The vehicle 100 schematically depicted in FIG. 1 has a pair of forward wheels 111, 112 and a pair of powered rear wheels 113, 114. It further has a power train with a prime mover 101 which may for example be a combustion engine, an electric motor or a combination of both, i.e. a so-called hybrid. The prime mover 101 may for example be connected in a conventional way, via an output shaft 102 leading from it, to a gearbox 103, possibly via a clutch 106. An output shaft 107 from the gearbox 103 drives the powered wheels 113, 114 via a final gear 108, e.g. a conventional differential, and driveshafts 104, 105 which are connected to said final gear 108. If for example the prime mover 101 takes the form of an electric motor, it may also be connected directly to the output shaft 107 or the driveshafts 104, 105.
A driver of the vehicle increasing a torque request to the prime mover 101 by, for example, input via an input means, e.g. by depressing an accelerator pedal, may cause a relatively rapid torque change in the power train. This torque is resisted by the powered wheels 113, 114 through their friction against the ground and the vehicle's rolling resistance. The driveshafts 104, 105 are thus subject to a relatively substantial twisting moment.
Inter alia for cost and weight reasons, the driveshafts are as a rule not dimensioned to cope with this substantial stress without being affected. Owing to their relative weakness, the driveshafts 104, 105 act instead like torsion springs between the powered wheels 103, 104 and the final gear 108.
When its rolling resistance is no longer sufficient to resist the torque from the power train, the vehicle 100 begins to roll, whereupon the torsion-springlike force in the driveshafts 103, 104 is released. When the vehicle moves off, this released force may result in power train oscillations, causing the vehicle to rock in the longitudinal direction, i.e. in its direction of movement. A driver of the vehicle is likely to find this rocking very unpleasant. He/she will prefer a gentle and pleasant driving experience such as to also create the impression that the vehicle is a refined and well-developed product. It is therefore necessary to be able to quickly detect and effectively damp out such power train oscillations.
Previous known solutions for damping of power train oscillations have been technically complicated, contributing to increased computational complexity and implementation cost. The previous known complicated solutions have also led to ineffective damping of these oscillations, with consequently unsatisfactory results as regards damping out power train oscillations.